A 2004 Snohomish County flood-management plan said the cost of buying Oso properties and removing residents from the path of a potential slide "would be significant, but would remove the risk to human life and structures."
But after weighing several options, the county instead recommended a project to shore up the base of the unstable hillside above the community about 55 miles north of Seattle, according to documents first reported by The Seattle Times.
A huge log wall was eventually built to reduce landslide and flood risks. But it wasn't enough to hold back the square mile of dirt, sand and silt that barreled down the hillside March 22, leveling homes and killing at least 30 people.
Some area residents and their family members say they knew nothing of the landslide danger or home-buyout proposals.
"There's never been any document that we've seen regarding that," said Irene Kuntz, whose sister Linda McPherson died in the landslide.
Kuntz said her father bought land in the area in 1940, and he "never was given any notice that it was in danger." Her son's home also was destroyed in the slide.
The Darrington woman said she didn't know whether they would have taken a buyout if offered.
A message left with Snohomish County Public Works director was not immediately returned. Heidi Amrine, a spokeswoman for the Joint Information Center for the landslide, said Thursday: "We don't have anyone who can address that right now."
Geologic reports noted previous landslides in the area and warned of a potential disaster.
In 2004, county officials evaluated three options, including voluntarily buying out properties at the base of the hillside that collapsed nearly two weeks ago.
The county based its options in part on a report by a consultant, GeoEngineers, who wrote that the landslide posed a "significant risk to human lives and private property, since human development of the flood plain in this area has steadily increased since the 1967 event."
GeoEngineers had warned in a 2000 draft study about "catastrophic failure," saying the river at the base of the landslide-prone hill was actively cutting into the slope.
That study, authored by Tracy Drury, weighed five alternatives, including buying out all the properties in flood-plain area and moving the Stillaguamish River about 2,000 feet from the slide. The cost of land purchases was estimated to be $1.6 million.
But the consultant said the likelihood that all property owners would be willing to sell was low, and so recommended a preferred option of providing "storage areas" in the flow path of the river to trap sediment from the slide. That option included buying out some properties.
A call to Drury was not returned Thursday. A woman who answered the phone at Drury's office Wednesday said Drury and others would not be available to comment.
Dale Dunshee, who sold his property in the neighborhood three years ago, told The Times: "If I'd known it was that dangerous, I would have moved in a heartbeat."
The county ultimately recommended implementing a project to stabilize the slope. While technically feasible, the plan noted that "stabilizing any large slide such as this is a difficult task."
A 1,300-foot crib wall was built in 2006.
Meanwhile, the number of confirmed deaths in the mudslide increased Thursday to 30, and the county medical examiner's office released two more victims' names. Gloria Halstead, 67, and Jovon E. Mangual, 13, both of Arlington, died of multiple blunt force injuries.
Associated Press researcher Rhonda Shafner in New York contributed to this report.